Nobel Laureate Warns Of Prions Found In Animal
Muscle
How Many Prions Does It Take To Become Infected?
By Richard Woodman
12-2-2

LONDON (Reuters Health) -
The scientist who won the Nobel prize for discovering prions, the abnormal
proteins implicated in mad cow disease, has called for all Britons to be
tested for the deadly brain ailment after finding surprisingly high prion
levels in the muscles of mice infected with a similar illness, British
newspapers reported Sunday.

Professor Stanley Prusiner of the University of California,
San Francisco, told the Independent that the finding raised the "obvious
worry" that cows and sheep could be similarly affected. Mad cow disease,
or bovine spongiform encephalopathy (BSE), has been linked to a similar
illness in humans who ate contaminated meat. Sheep can carry a related
illness called scrapie.

Until now, levels of prions in infected cow and sheep
meat and muscle tissue were always believed to be low enough not to pose
a significant risk of transmission and the emphasis was to remove the brain
and spinal cord, which harbor much higher levels.

However, according to the newspaper, new tests being
pioneered at the University of California are far more sensitive and have
discovered higher concentrations of prions in muscle than have previously
been found.

While describing the findings as significant, Prusiner
stressed that the levels are still 100-fold less than those found in brains.

He called for testing of everyone in Britain to establish
the true extent of variant Creutzfeldt-Jakob disease (CJD), which has killed
117 people since 1995.

"A million cattle infected with BSE entered the
British food chain so almost everyone in the country will have been exposed
to the infectious prion proteins that cause variant CJD. Every Briton should
be tested so that if they are developing the disease it can be spotted
before symptoms appear," he told the Sunday Times.

Prusiner was in Britain to discuss research into the
disease.

Last week scientists at University College London reported
that research on mice suggested BSE caused the "sporadic" strain
of CJD, as well as variant CJD, which, if confirmed, could significantly
increase the number of potential victims.